Implantable neurostimulator-implemented method for enhancing heart failure patient awakening through vagus nerve stimulation

Abstract

An implantable neurostimulator-implemented method for managing tachyarrhythmias upon a patient's awakening from sleep through vagus nerve stimulation is provided. An implantable neurostimulator, including a pulse generator, is configured to deliver electrical therapeutic stimulation in a manner that results in creation and propagation (in both afferent and efferent directions) of action potentials within neuronal fibers comprising the cervical vagus nerve of a patient. Operating modes of the pulse generator are stored. An enhanced dose of the electrical therapeutic stimulation is parametrically defined and tuned to prevent initiation of or disrupt tachyarrhythmia upon the patient's awakening from a sleep state through at least one of continuously-cycling, intermittent and periodic ON-OFF cycles of electrical pulses. Other operating modes, including a maintenance dose and a restorative dose are defined. The patient's physiological state is monitored via at least one sensor to detect that patient's awakening, which activates the delivery of the enhanced dose.

What is claimed is: 
     
       1. A method for aiding awakening-induced tachyarrhythmias through vagus nerve stimulation, comprising the steps of:
 providing an implantable neurostimulator comprising a sensor and a pulse generator configured to deliver electrical therapeutic stimulation to a vagus nerve of a patient; 
 storing an operating mode of the pulse generator in a memory, the operating mode defining:
 a first dose of the electrical therapeutic simulation comprising a first intensity; and 
 a second dose of the electrical therapeutic stimulation comprising a second intensity lower than the first intensity; 
 
 monitoring a physiological state of the patient to sense a patient's awakening from a sleep state via the sensor; and 
 upon sensing the patient's awakening, delivering the first dose to the vagus nerve. 
 
     
     
       2. A method according to  claim 1 , further comprising delivering the second dose to the vagus nerve via the pulse generator through a pair of helical electrodes following the delivery of the first dose. 
     
     
       3. A method according to  claim 1 , wherein the sensor comprises a heart rate sensor, the method further comprising the steps of:
 establishing a normative heart rate of the patient with the heart rate sensor as a mean heart rate sensed during the sleep state; 
 sensing a heart rate of the patient with the heart rate sensor; and 
 confirming that the patient is awakening from the sleep state when the heart rate gradually rises and is sustained at an elevated heart rate above the normative heart rate. 
 
     
     
       4. A method according to  claim 1 , wherein the sensor comprises an accelerometer, the method further comprising the steps of:
 establishing a normative activity level of the patient with the accelerometer as a mean frequency of movement sensed during the sleep state; 
 sensing the patient's activity level with the accelerometer; and 
 confirming that the patient is awakening from the sleep state when the patient's activity level rises and is sustained at an elevated activity level above the normative activity level. 
 
     
     
       5. A method according to  claim 1 , wherein the sensor comprises a minute ventilation sensor, the method further comprising the steps of:
 establishing a normative tidal volume and normative respiratory rate of the patient with the minute ventilation sensor sensed during the sleep state; 
 sensing the patient's tidal volume and respiratory rate with the minute ventilation sensor; and 
 confirming that the patient is awakening from the sleep state with the patient's tidal volume and respiratory rate rise and are sustained at elevated levels respectively above the normative tidal volume and the normative respiratory rate by a threshold amount. 
 
     
     
       6. A method according to  claim 1 , further comprising monitoring the physiological state through delivery of the first dose and, upon sensing a condition indicative of an onset of tachyarrhythmia, intensifying the electrical therapeutic stimulation as specified in the operating mode. 
     
     
       7. A method according to  claim 6 , further comprising progressively intensifying the electrical therapeutic stimulation as specified in the operating mode as the tachyarrhythmia continues. 
     
     
       8. A method according to  claim 6 , further comprising increasing the electrical therapeutic stimulation to a highest level specified in the operating mode in response to the tachyarrhythmia failing to respond to the intensified electrical therapeutic stimulation. 
     
     
       9. A method according to  claim 1 , further comprising extending a period of time of the first dose delivery based on a heart response trajectory of the patient determined by a processor of the neurostimulator using data from the sensor. 
     
     
       10. A method according to  claim 1 , further comprising progressively intensifying the electrical therapeutic stimulation as specified in the operating mode independently of the patient's heart response trajectory. 
     
     
       11. A method according to  claim 1 , further comprising the steps of:
 electrically stimulating the vagus nerve after an expiration of a period of time, comprising the steps of:
 monitoring the physiological state of the patient to detect a presence or an absence of the condition indicative of tachyarrhythmia; 
 upon detecting the presence of the condition indicative of the tachyarrhythmia after an expiration of the period of time, switching to delivering a third dose to the vagus nerve via the pulse generator; and 
 upon detecting the absence of the condition indicative of the tachyarrhythmia after an expiration of the period of time, switching to delivering the second dose to the vagus nerve via the pulse generator, 
 
 wherein the storing of the operating modes of the pulse generator further comprises defining the third dose of the electrical therapeutic simulation tuned to prevent initiation of or disrupt tachyarrhythmia. 
 
     
     
       12. A method according to  claim 11 , wherein the third dose comprises periodic electrical pulses delivered at a higher intensity than the second dose. 
     
     
       13. A method according to  claim 11 , further comprising the steps of:
 defining the intensity of the first dose as comprising one or more of an output current, a duty cycle, a frequency, and a pulse width; 
 defining the second dose as comprising one or more of an output current lower than the first dose output current, a duty cycle lower than the first dose duty cycle, a frequency lower than the first dose frequency, and a pulse width shorter than the first dose pulse width; and 
 defining the third dose as comprising one or more of an output current higher than the second dose output current, a duty cycle higher than the second dose duty cycle, a frequency higher than the second dose frequency, and a pulse width longer than the second dose pulse width. 
 
     
     
       14. A method according to  claim 11 , further comprising the steps of:
 providing a magnetically-actuated reed switch configured to control the pulse generator; and 
 controlling the pulse generator in response to a magnetic signal remotely applied to the reed switch by at least one of:
 switching between delivery of the first dose, the second dose, and the third dose; 
 triggering or increasing delivery of either the first dose, the second dose, and the third dose; and 
 decreasing or suspending delivery of either of the first dose, the second dose, and the third dose. 
 
 
     
     
       15. A method according to  claim 1 , further comprising titrating the electrical therapeutic stimulation when beginning or suspending delivery of the first dose. 
     
     
       16. A method according to  claim 1 , wherein defining the first dose further comprises:
 monitoring the patient's normative physiology during delivery of the first dose; and 
 suspending the electrical therapeutic stimulation as specified in the operating mode upon a presence of a bradyarrhythmia. 
 
     
     
       17. A neurostimulator system for aiding awakening-induced tachyarrhythmias through vagus nerve stimulation, comprising:
 a sensor; and 
 a neurostimulator comprising a pulse generator configured to deliver electrical therapeutic stimulation to a patient's vagus nerve and a memory comprising instructions that cause the pulse generator to:
 deliver a first dose of the electrical therapeutic stimulation at a first intensity; 
 deliver a second dose of the electrical therapeutic stimulation at a second intensity lower than the first intensity; 
 monitor the physiological state of the patient to sense a patient's awakening from a sleep state via the sensor; and 
 upon sensing the patient's awakening, delivering the first dose to the vagus nerve. 
 
 
     
     
       18. A system according to  claim 17 , wherein the pulse generator further comprises a pair of helical electrodes configured to deliver the first dose and the second dose to the vagus nerve. 
     
     
       19. A system according to  claim 17 , wherein the memory further comprises instructions that cause the pulse generator to monitor the physiological state throughout the delivery of the first dose and, upon sensing a condition indicative of an onset of tachyarrhythmia, intensifying the electrical therapeutic stimulation. 
     
     
       20. A system according to  claim 17 , wherein the memory further comprises instructions that cause the pulse generator to:
 electrically stimulate the cervical vagus nerve after an expiration of the period of time, comprising the steps of:
 upon detecting the presence of the condition indicative of the tachyarrhythmia after an expiration of the period of time, switch to delivering a third dose to the vagus nerve via the pulse generator; and 
 upon detecting an absence of the condition indicative of the tachyarrhythmia after an expiration of the period of time, switch to delivering the second dose to the vagus nerve via the pulse generator, 
 
 wherein the storing of the operating modes of the pulse generator further comprises defining the third dose of the electrical therapeutic simulation tuned to prevent initiation of or disrupt tachyarrhythmia.